Medicine & Science in Sports & Exercise

Exercise Intensity Matters in Chronic Nonspecific Low Back Pain Rehabilitation Introduction Exercise therapy (ET) is advocated as a treatment for chronic nonspecific low back pain (CNSLBP). However, therapy effect sizes remain low. In other chronic disorders, training at higher intensity has resulted in greater improvements on both general health related and disease specific outcomes compared to lower intensity ET. Possibly, high intensity training also improves effect sizes in CNSLBP. Objective To compare the effects of a high intensity ET program with a similar moderate intensity ET program on disability, pain, function, exercise capacity, and abdominal/back muscle strength in persons with CNSLBP. Methods In a randomized controlled trial, persons with CNSLBP performed a 12-week ET program (24 sessions, 1.5hours/session, 2x/week) at high (HIT) or moderate intensity (MIT). Questionnaires to assess disability (Modified Oswestry Index (MODI)), pain intensity (Numeric Pain Rating Scale (NPRS)), and function (Patient Specific Functioning Scale (PSFS)), a cardiopulmonary exercise test to assess exercise capacity (VO2max, cycling time), and a maximum isometric muscle strength test to assess abdominal/back muscle strength (maximum muscle torque) were administered at baseline and after the training program. Results Thirty-eight participants (HIT: n=19, MIT: n=19) were included (mean age: 44.1y, SD=9.8, 12 males). Groups did not differ at baseline. Between group differences (p<0.01) in favor of HIT were found for MODI, VO2max, and cycling time. Within group improvements (p<0.01) were found in both groups on MODI (HIT:-64%, MIT:-33%), NPRS (HIT:-56%, MIT:-39%), PSFS (HIT:+37%, MIT:+39%), VO2max (HIT:+14, MIT:+4%), cycling time (HIT:+18%, MIT:+13%), and back muscle strength (HIT:+10%, MIT:+14%). Conclusion HIT proved to be a feasible, well tolerated, and effective therapy modality in CNSLBP. Moreover, it shows greater improvements on disability and exercise capacity than a similar ET performed at moderate intensity. Corresponding author: Jonas Verbrugghe, Hasselt University, Faculty of Rehabilitation Sciences, REVAL, Gebouw A, Agoralaan 5, 3590, Diepenbeek, Belgium, Tel: +003211269239, jonas.verbrugghe@uhasselt.be This project is funded by the UHasselt research fund BOF New initiatives (project number R-5211). This funding source had no role in the design of this study and will not have any role during its execution, analyses, interpretation of the data, or decision to submit results. The authors would like to thank all the persons with CNSLBP that participated in this study. Conflict of Interest. The authors report no conflict of interest. Accepted for Publication: 24 June 2019 © 2019 American College of Sports Medicine

Lower Trapezius Weakness and Shoulder Complex Biomechanics during the Tennis Serve PURPOSE This study aimed to assess the effect of lower trapezius (LT) weakness on humeral and scapular kinematics and shoulder muscle activity during the tennis serve. METHODS Fifteen competitive male tennis players (age: 23.8 ± 3.4 years; height: 182.8 ± 6.7 cm; mass: 76.6 ± 8.7 kg; tennis experience: 15.6 ± 4.9 years) performed two tennis serves before and after selective fatigue of the LT (25-min electric muscle stimulation). During each tennis serve, racket, humeral and scapular kinematics and the activity of 13 shoulder muscles were recorded using an optoelectronic system synchronized with indwelling and surface electromyography. The serve was split into five phases, i.e., early and late cocking, acceleration, early and late follow-through. RESULTS Selective fatigue led to a 22.5 ± 10.4% strength decrease but did not alter maximum racket speed and humerothoracic joint kinematics. However, increased scapular upward rotation was observed in the acceleration (p=0.02) and early follow-through (p=0.01) phases. Decreased muscular activity was observed during the early cocking phase for the LT (p=0.01), during the acceleration phase for the LT (p=0.01), anterior deltoid (p=0.03), pectoralis major (p=0.04) and subscapularis (p=0.03), and during the early follow-through phase for the anterior deltoid (p=0.03) and LT (p=0.04). CONCLUSION LT weakness altered neither serve velocity nor humerothoracic joint kinematics, but impaired scapulothoracic kinematics and anterior shoulder muscle activation. Such alterations may reduce the subacromial space and jeopardize humeral head stability. These findings shed new light on the consequences of LT weakness, highlighting the importance of monitoring and strengthening this muscle in overhead athletes. Corresponding author: Isabelle Rogowski, UCB Lyon 1 – UFRSTAPS, 27-29, bd du 11 novembre 1918, 69622 Villeurbanne Cedex France, E-mail: isabelle.rogowski@univ-lyon1.fr This study was supported by Auvergne-Rhône-Alpes with the explora'doc program and by Mitacs with the globalink program. Conflict of interest. The authors declare no conflict of interest. Accepted for Publication: 21 June 2019 © 2019 American College of Sports Medicine

Reduced Active Muscle Stiffness after Intermittent Submaximal Isometric Contractions Purpose Whether muscle stiffness is influenced by fatigue remains unclear. Classical methods used to assess muscle stiffness provide a global measure at the joint level. As fatigue may selectively affect specific muscles, a joint-level approach may not be sensitive enough to detect potential changes in muscle stiffness. Taking advantage of ultrasound shear wave elastography, this study aimed to determine the influence of a fatiguing protocol involving intermittent submaximal isometric contractions on muscle shear modulus (an index of stiffness). Methods Shear modulus was measured on either the vastus lateralis (VL; n=9) or the abductor digiti minimi (ADM; n=10) before and after 15-mins of intermittent submaximal isometric contractions at 60% of maximal voluntary contraction (MVC; 4 s ON, 4 s OFF). An index of active muscle stiffness was estimated PRE and POST-fatigue as the slope of the linear regression established between shear modulus and absolute joint force up to 60% MVC. Results After the fatiguing exercise, MVC was significantly decreased by 22 ± 7 % and 32 ± 15 % for knee extension and little finger abduction, respectively (p<0.001). When compared to PRE-fatigue, the index of active muscle stiffness was 12 ± 15 % lower for the VL (p < 0.031) and 44 ± 19 % lower for the ADM (p < 0.001) POST-fatigue. Conclusion Although the present results cannot clearly determine the involved mechanisms, they demonstrate a decreased active muscle stiffness after a fatiguing task involving intermittent submaximal isometric contractions. Further studies should now determine whether this change in stiffness affects performance and risk of injury. CORRESPONDING AUTHOR: Thomas LAPOLE, Laboratoire Interuniversitaire de Biologie de la Motricité, Bâtiment IRMIS, 10 rue de la Marandière, 42270 Saint Priest en Jarez, thomas.lapole@univ-st-etienne.fr The authors declare they have no conflict of interest. The authors did not receive any funding for this study. The results of the study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation. The results of the present study do not constitute endorsement by ACSM. Accepted for Publication: 21 June 2019 © 2019 American College of Sports Medicine

High-Intensity Interval Training is Feasible in Women at High Risk for Breast Cancer Purpose This trial aimed to demonstrate feasibility of high-intensity interval training (HIIT) in post-menopausal, overweight/obese women at high-risk of invasive breast cancer, and explore HIIT on changes in cardiorespiratory fitness (CRF), body weight, and body mass index (BMI) compared to moderate-intensity continuous training (MICT) and usual care (UC). Methods Forty-four women were randomized to HIIT, MICT or UC for a 12-week, thrice weekly, supervised exercise intervention. HIIT included a 5-minute warm-up at 50-70% peak heart rate (HR), four cycles of four minutes at 90-100% peak HR followed by three minutes at 50-70% peak HR. MICT consisted of 41 minutes at 60-70% peak HR. Feasibility was assessed by consent, adherence, compliance and retention rates. CRF, body weight and BMI were measured at baseline and end-of-study. Repeated measures linear mixed models were used to assess within- and between-group differences. Results Average age was 63.9±8.8 years. BMI was 30.9±5.7 kg/m2. Participants completed 90% and 89% of HIIT and MICT workouts respectively, with 100% compliance to the exercise prescriptions. No serious adverse events were reported. Compared to MICT and UC, HIIT exhibited improvements in change in treadmill time (101 seconds greater than MICT, and 125 seconds greater than UC, respectively, p<0.001). Compared to UC, HIIT exhibited improvement in changes in absolute and relative VO2peak (a 0.15 increase in L/min, p=0.005; and 2.3 increase in ml/kg/min, p=0.004). There were no significant differences between groups for body weight or BMI (p>0.05). Conclusions HIIT is feasible, safe, and appears to promote greater improvements in CRF compared to MICT and UC in women at high risk for breast cancer. Correspondence: Susan C Gilchrist, MD; The University of Texas MD Anderson Cancer Center, 1155 Pressler Street, Unit 1360, Houston TX 77230-1439; Phone: 713-745-6251; Fax: 713-794-4403; sgilchrist@mdanderson.org The authors thank the NCI R25 Cancer Prevention Research Training Program (CA057730, PI: Shine Chang PhD), the MD Anderson Cancer Center/Energy Balance Assessment Supplemental Funding (PI: Susan Gilchrist MD), and the MD Anderson Cancer Center, Center for Energy Balance in Cancer Prevention and Survivorship. The authors declare that they have no conflicts of interest to disclose. The results of the present study do not constitute endorsement by the ACSM, and are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation. Accepted for publication: 10 May 2019. This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND), where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially without permission from the journal. © 2019 American College of Sports Medicine

Data-informed Intervention Improves Football Technique and Reduces Head Impacts Introduction Although sport participation is a key contributor to the physical and mental health of children and youth, exposure to sub-concussive head impacts in football has raised concerns about safety for athletes. Purpose To demonstrate the efficacy of incorporating targeted football drills into a team's practice routine with the goal of improving players' technique, and reduce exposure to sub-concussive head impacts. Methods Seventy high-school football players (age=16.4±1.1years) were tested PRE-season using a sport-specific functional assessment. Results from the testing were used to inform the design of a pre-practice intervention aimed at improving tackling and blocking techniques, while reducing exposure to head impacts. The assessment included drills which evaluated the players' ability to safely tackle, and block, while simulating game-like situations. Testing was repeated at MID-season (internal control) without an intervention, and again at POST-season (experimental), following introduction of the pre-practice intervention between these timepoints, administered twice weekly. All testing sessions were recorded, and subsequently reviewed by trained graders based on selected criteria defined by football coaches. A subset of nineteen participants wore in-helmet accelerometers to assess the effectiveness of the intervention in decreasing head impacts during practice. Results Significant improvements in blocking and tackling techniques were observed following the introduction of the intervention (P<0.0001). Participating athletes also showed better techniques when evaluated in new game-like situations, post-season, providing evidence for proper acquisition and generalizability of these safer habits. Finally, frequency of head impacts (>15g) per practice was significantly reduced by ~30% after one month of training. Conclusion Our results suggest that data-informed methods can be used to improve coaching practices, and promote safer play, which can have a positive public health impact moving forward. Corresponding author: Douglas J. Cook, Department of Surgery, Queen's University, Room 232, 18 Stuart St. Kingston, ON K7L 3N6. Phone: 613-549-6666 ext. 3696. Fax: 613-548-1346. dj.cook@queensu.ca Results from this study are presented clearly, honestly and without fabrication, falsification, or inappropriate data manipulation. Results of the present study do not constitute endorsement by the American College of Sports Medicine. The authors declare no conflict of interest. Funding from the Southeastern Ontario Academic Medical Organization (SEAMO) helped making this project possible. Accepted for publication: 7 May 2019. This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND), where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially without permission from the journal. © 2019 American College of Sports Medicine

Motor Strategies Learned during Pain Are Sustained upon Pain-free Re-exposure to Task Introduction Pain affects movement planning and execution, and may interfere with the ability to learn new motor skills. Variations among previous studies suggest task-specific effects of pain on the initial acquisition and subsequent retention of motor strategies. Methods The present study assessed how acute pain in the anterior deltoid muscle affects movement accuracy of fast arm-reaching movements during force field perturbations, and upon immediate pain-free repetition of the same task. Results Despite having slower initial rate of improvement, individuals who experienced pain during training achieved the same final performance as pain-free controls. However, pain altered the strategy of muscle activation adopted to perform the task, which involved less activity of the shoulder and arm muscles. Strikingly, motor strategies developed during the first exposure to the force field were retained upon re-exposure to the same perturbation, after resolution of pain. Conclusion Although reduced muscle activation may be interpreted as metabolically efficient, it reduces joint stability and can have negative consequences for joint integrity. These results demonstrate that alternative motor strategies developed in the presence of pain can be maintained when training is resumed after resolution of pain. This effect could have deleterious consequences if it applies when learning motor skills in sports training and rehabilitation. Corresponding author: Dr Paul W. Hodges, School of Health and Rehabilitation Sciences, The University of Queenslandm, Brisbane QLD 4072, Australia, Phone: +61 7 3365 2008, E-mail: p.hodges@uq.edu.au Disclosures and Acknowledgements This study was funded by a Program Grant (APP1091302), a Senior Principal Research Fellowship (APP1102905) from the National Health and Medical Research Council (NHMRC) of Australia, and a Future Fellowship grant to TC (FT120100391). The authors have no conflicts of interest to declare. All the authors are properly listed, and all have contributed substantially to the manuscript. The results of the study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation, and statement that results of the present study do not constitute endorsement by ACSM. Accepted for Publication: 29 May 2019 © 2019 American College of Sports Medicine

Cytokine and Sclerostin Response to High-Intensity Interval Running versus Cycling Purpose This study examined whether the exercise-induced changes in inflammatory cytokines differ between impact and no-impact high intensity interval exercise, and whether they are associated with post-exercise changes in sclerostin. Methods Thirty-eight females (n=19, 22.6±2.7 years) and males (n=19, 22.3±2.4 years) performed two high-intensity interval exercise trials in random order (cross-over design): running on a treadmill and cycling on a cycle ergometer. Trials consisted of eight repetitions of 1 min running or cycling at ≥90% maximal heart rate, separated by 1 min passive recovery intervals. Blood was collected pre-exercise, and 5 min, 1h, 24h and 48h post-exercise, and was analyzed for serum levels of interleukins (IL-1β, IL-6, IL-10), tumor necrosis factor alpha (TNF-α) and sclerostin. Results Inflammatory cytokines significantly increased over time in both sexes with some differences between trials. Specifically, IL-1β significantly increased from pre- to 5 min after both trials (23%, p<0.05), IL-6 increased 1h following both trials (39%, p<0.05), IL-10 was elevated 5 min after running (20%, p<0.05) and 1h after both running and cycling (41% and 64%, respectively, p<0.05), and TNF-α increased 5 min after running (10%, p<0.05). Sclerostin increased 5 min following both trials, with a greater increase in males than in females (62 vs 32 pg/ml in running, p=0.018; 63 vs 30 pg/ml in cycling, p=0.004). In addition, sclerostin was significantly correlated with the corresponding changes in inflammatory cytokines and 34% of the variance in its post-exercise gain score (Δ) was explained by sex and the corresponding gain scores in TNF-α, which was the strongest predictor. Conclusion A single bout of either impact or no-impact high-intensity exercise induces changes in inflammatory cytokines, which are associated with the post-exercise increase in sclerostin. Corresponding author: Panagiota Klentrou Department of Kinesiology Faculty of Applied Health Sciences Brock University 1812 Sir Isaac Brock Way St. Catharines, ON, L2S 3A1, Canada E-mail: nklentrou@brocku.ca This study was funded by a National Science Engineer Research Council of Canada (NSERC) grant to P. Klentrou (grant # 2015-04424). R. Kouvelioti holds an Ontario Trillium Scholarship. N. Kurgan holds an NSERC Doctoral Scholarship. W. Wards holds a Canada Research Chair in Bone and Muscle Development. The results of the study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation. The results of the present study do not constitute endorsement by ACSM. Conflicts of interest: The authors have no conflict of interest to declare. Accepted for publication: 14 June 2019. © 2019 American College of Sports Medicine

Extended Sleep Maintains Endurance Performance better than Normal or Restricted Sleep Purpose The cumulative influence of sleep time on endurance performance remains unclear. This study examined effects of three consecutive nights of both sleep extension and restriction on endurance cycling performance. Methods Endurance cyclists/triathletes (n=9) completed a counterbalanced crossover experiment with three conditions; sleep restriction (SR), normal sleep (NS), and sleep extension (SE). Each condition comprised seven days/nights of data collection (-2, -1, D1, D2, D3, D4, +1). Sleep was monitored using actigraphy throughout. Participants completed testing sessions on days D1-D4 that included an endurance time-trial (TT), mood, and psychomotor vigilance assessment. Perceived exertion (RPE) was monitored throughout each TT. Participants slept habitually prior to D1, however, time in bed was reduced by 30% (SR), remained normal (NS), or extended by 30% (SE) on nights D1, D2, and D3. Data were analysed using Generalised Estimating Equations. Results On nights D1, D2, and D3, total sleep time was longer (P<0.001) in the SE condition (8.6±1.0; 8.3±0.6; 8.2±0.6h, respectively), and shorter (P<0.001) in the SR condition (4.7±0.8; 4.8±0.8; 4.9±0.4h) compared with NS (7.1±0.8; 6.5±1.0; 6.9±0.7h). Compared with NS, TT performance was slower (P<0.02) on D3 of SR (58.8±2.5 vs 60.4±3.7min) and faster (P<0.02) on D4 of SE (58.7±3.4 vs 56.8±3.1min). RPE was not different between or within conditions. Compared with NS, mood disturbance was higher-, and psychomotor vigilance impaired, following SR. Compared with NS, psychomotor vigilance improved following SE. Conclusion Sleep extension for three nights led to better maintenance of endurance performance compared with normal and restricted sleep. Sleep restriction impaired performance. Cumulative sleep time affects performance by altering the perceived exertion of a given exercise intensity. Endurance athletes should sleep >8 hours per night to optimise performance. Corresponding author: Spencer S. H. Roberts, PhD Candidate School of Exercise and Nutrition Sciences, Deakin University. 221 Burwood Hwy, Burwood, Victoria, Australia, 3125 Email: rspen@deakin.edu.au The results of this study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation. Results do not constitute endorsement by the American College of Sports Medicine. Spencer Roberts, Wei-Peng Teo, Brad Aisbett, and Stuart Warmington declare they have no conflict of interest. The authors acknowledge the School of Exercise and Nutrition Sciences at Deakin University for funding the study. Accepted for publication: 9 June 2019. © 2019 American College of Sports Medicine

Methodological Recommendations for Menstrual Cycle Research in Sports and Exercise Introduction The aim of this review is to provide methodological recommendations for menstrual cycle research in exercise science and sports medicine based on a review of recent literature. Research in this area is growing, but often reports conflicting results and it is proposed that some of this may be explained by methodological issues. Methods This review examined the menstrual cycle verification methodologies used in recent literature on exercise performance over the menstrual cycle identified through a literature search of PubMed and SportDiscus from 2008 until 2018. Results Potential changes over the menstrual cycle are likely related to hormone fluctuations, however, only 44% of the selected studies measured the actual concentrations of the female steroid hormones estrogen and progesterone. It was shown that the likely inclusion of participants with anovulatory or luteal phase deficient cycles in combination with small participant numbers has impacted results in recent menstrual cycle research and consequently our understanding of this area. Conclusion To improve the quality of future menstrual cycle research it is recommended that a combination of three methods is used to verify menstrual cycle phase: the calendar-based counting method combined with urinary luteinizing hormone surge testing and the measurement of serum estrogen and progesterone concentrations at the time of testing. A strict luteal phase verification limit of >16 nmol·L-1 for progesterone should be set. It is also recommended that future research focusses on the inclusion of the late follicular estrogen peak. It is envisaged that these methodological recommendations will assist in clarifying some of the disagreement around the effects of the menstrual cycle on exercise performance and other aspects of exercise science and sports medicine. Corresponding author: Xanne Janse de Jonge Exercise & Sport Science Faculty of Science The University of Newcastle, Australia Central Coast Campus PO Box 127 Ourimbah NSW 2258 Australia E: X.Jansedejonge@newcastle.edu.au ORCID 0000-0003-3657-5298 Xanne Janse de Jonge, Belinda Thompson and Ahreum Han declare that they have no conflicts of interest relevant to the content of this review. The results of the present study do not constitute endorsement by ACSM. The results of this review are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation. No funding was received for this review. Accepted for publication: 22 May 2019. © 2019 American College of Sports Medicine

Estimated Cardiorespiratory Fitness and Risk of Atrial Fibrillation: The HUNT Study Purpose To investigate the association between estimated cardiorespiratory fitness (eCRF) and risk of atrial fibrillation (AF), and examine how long-term changes in eCRF affects the AF risk. Methods This prospective cohort study includes data of 39 844 men and women from the HUNT2 (August 15, 1995 - June 18, 1997) and the HUNT3 study (October 3, 2006 – June 25, 2008). The follow-up period was from HUNT3 until AF diagnosis or November 30, 2015. AF diagnoses were retrieved from hospital registers and validated by medical doctors. A non-exercise test based on age, waist circumference, resting heart rate and self-reported physical activity was used to estimate CRF. Cox regression was performed to assess the association between eCRF and AF. Results The mean age was 50.6 ± 14.6 years for men and 50.2 ± 15.2 years for women. Mean follow-up time was 8.1 years. 1 057 cases of AF were documented. For men, the highest risk reduction of AF was 31% in the 4th quintile of eCRF when compared to the 1st quintile (HR, 0.69; 95% CI, 0.53-0.89). For women, the highest risk reduction was 47% in the 5th quintile when compared to the 1st quintile (HR, 0.53; 95% CI, 0.38-0.74). One metabolic equivalent increase in eCRF over a 10-year period was associated with 7% lower risk of AF (HR, 0.93; 95% CI, 0.86-1.00) Participants with improved eCRF had 44% lower AF risk compared to those with decreased eCRF (HR, 0.56; 95% CI, 0.36-0.87). Conclusion eCRF was inversely associated with AF, and participants with improved eCRF over a 10-year period had less risk of AF. These findings support the hypothesis that fitness may prevent AF. Correspondence and reprints to: Lars E. Garnvik, Department of Circulation and Medical Imaging, NTNU, Medisinsk Teknisk Forskningssenter, Post box 8905, 7491 Trondheim, Norway. E-mail: lars.e.garnvik@ntnu.no This work was supported by grants from the The Liaison Committee for education, research and innovation in Central Norway. The results of the study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation, and statement that results of the present study do not constitute endorsement by ACSM. The Nord-Trøndelag Health Study (The HUNT Study) is a collaboration between HUNT Research Centre, (Faculty of Medicine and Health Sciences, NTNU, Norwegian University of Science and Technology), Trøndelag County Council, Central Norway Regional Health Authority, and the Norwegian Institute of Public Health. We would like to thank all the participants and technicians of the HUNT study for their contributions. Conflict of interest: None declared. Accepted for publication: 14 June 2019. © 2019 American College of Sports Medicine

Alexandros Sfakianakis
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